As U.S. lawmakers debate whether to continue an American spy agency’s massive collection of telephone metadata or approve a less intrusive version, experts say the program may not be as critical as it was once thought to be.

The collection program falls under section 215 of the Patriot Act, which was passed in the panic-filled aftermath of the September 11, 2001, terrorist attacks.

The U.S. House of Representatives overwhelmingly passed legislation Wednesday that extends the Patriot Act. But the measure may face a rockier road in the Senate.

One former senior intelligence official, speaking to VOA on condition of anonymity, acknowledged priorities have changed.

“There may be a sense that it may not be as important as we thought it was going to be in 2001, 2002,” the former official said in a telephone interview. Moreover, he said, the line between civil liberties and security has also shifted.

“The country saw the line very differently on September 13, 2001, in which case I think there was a sense of ‘do whatever you have to do,’” he said. “I think the country has dialed back a little bit, perhaps because we’ve not had any terrorist attack.”

Not the critical tool it was

Supporters of the National Security Agency’s bulk collection have said it is an important tool to prevent terrorist attacks. Critics believe it is a violation of Americans’ civil liberties.

In 2001, mobile phones were widely used by al-Qaida and other terrorist networks.

The U.S. military has used satellite and cell phone signals to help locate targets. Today, terrorists are aware they can be tracked through cell phone calls, and leaders of groups like the Islamic State have warned their followers of the risks.

As a result, terrorists and their supporters use a medley of different electronic communication tools, such as WhatsApp, SnapChat, TextSecure, Twitter, Kik, ChatSecure, Telegram, RedPhone, Silent Phone, several of which offer “destruct” features after use. They also discuss the latest technologies to avoid being detected by government-led content surveillance.

Carrie Cordero, Director of National Security Studies at Georgetown Law, says despite the attention the Section 215 bulk telephone metadata collection is getting, it is less relevant in the U.S. counterterrorism effort than it used to be.

“Is it the most valuable program? Probably not,” Cordero told VOA. But she adds that national security leaders say it is still useful.

“They are not asserting that it’s the most productive collection program that exists, but that it was intended to fill a particular gap that was identified after September 11 [2001], and that it’s an insurance policy to ensure that that gap doesn’t occur again.”

A federal appeals court in early May declared the bulk gathering of phone data as illegal, on the basis that collecting such a high volume of phone records strained the reasonable definition of what is relevant to a particular investigation.

How bulk collection is used

Gregory Nojeim, senior counsel in the Center for Democracy and Technology, said Section 215 - the authority under which U.S. intelligence agencies collect data on telephone numbers of calls to, from and within the United States, and which was due to expire on June 1 - was used as a doorway into even broader and more intrusive surveillance techniques.

“Section 215 is collecting a lot of records, I don’t want to understate that,” Nojeim told VOA, and added that “it is used to identify potential targets for more invasive surveillance, including communications content surveillance.

This is how it works: the FBI or NSA collect phone call records, then run a particular number against those records. Once they find what number has been calling what number, they can establish networks and patterns of phone calls. That information is then used to help them decide whom to target under a different part of the Patriot Act, known as Section 702.

Under Section 702, surveillance has to be targeted, that is, it has to be “selector-based,” meaning either a particular email or phone number. Once that is established, the content of the information associated with that email or phone number can be collected and surveilled. That would include social media, texts, emails and other modes of communication.

Section 702, Nojeim said, “is a particularly difficult statute because it involves surveillance conducted in the United States of people outside the United States by compelling U.S. providers to turn over their communications content.”

But there is more. Even though Section 702 cannot be used to target Americans, it is used to target foreigners who may speak with Americans.

“What the statute is being used for is to compel a U.S. provider to, for example, turn over all the emails to or from a particular email address that is associated with a non-U.S. person abroad. Those emails may well include the communications of people who are in the United States or people who are Americans,” explained Nojeim.

As yet, Congress has not focused on this statute, which is not due to expire until 2017.

“Those types of content-based collections, I think government officials have said, are probably the most valuable means of collecting signals intelligence,” Cordero said.

Executive Order 12333

Even if that statute comes under fire, intelligence agencies can also collect information on leads developed through Section 215 with another tool in their surveillance tool box: Executive Order 12333. That EO was first issued by President Ronald Reagan to govern surveillance and other intelligence techniques used to collect foreign intelligence information.

According to Nojeim, the EO 12333 definition of foreign intelligence information is so broad that it imposes no meaningful restriction on surveillance of people outside the United States. Under the Order, any activity of a foreign person, whether or not tied to a foreign government, qualifies as foreign intelligence information and can also be collected in bulk.

“When collection is done in bulk, more and more communications of people who have nothing to do with a foreign government, foreign terrorist organization, who have nothing to do with spying or espionage, gets collected, including the communications of Americans,” Nojeim said.

The volume of the NSA’s mass surveillance and bulk telephone metadata gathering became public after it was leaked by Edward Snowden to The Guardian newspaper. Critics said the breadth of the surveillance surpassed the intention of the law.

But what if...

Bob Litt, general counsel in the Office of the Director of National Intelligence acknowledged last week that the intelligence community needs to be more transparent about its work if it wants to maintain public support.

But he insisted there has to be a balance between transparency and security. “The fact of the matter is the more you authorize release of information about specifically what we are doing, the more you enable people to evade what we’re doing, and that is the balance that has to be struck in any kind of legislation like this.”

The former senior intelligence official who agreed to speak to VOA agreed with that assessment, and said if the US public felt more comfortable with its government dialing back its intelligence, that was its decision.

But, he warned, “If we dial it back, if it turns out we dialed back too far in the other direction, and something happens, I would like Congress to stand up and take responsibility for that instead of blaming it on the intelligence services.”

Sharon Behn is a foreign correspondent working out of Voice of America’s headquarters in Washington D.C Her current beat focuses on political, security and humanitarian developments in Iraq, Syria and Turkey. Follow Sharon on Twitter and on Facebook.